Existing reverse camera, new head unit

We've replaced the Japanese language, Toyota branded fujitsu ten head unit in our 2000 importToyota Estima, with a new, English language, Toyota branded Fujitsu ten head unit.

It's a newer unit and the big Toyota 10-pin + 6-pin plug for the power and speaker wires is the same, but all of the other connectors are different.

Everything works, except the reversing camera.
The problem is we don't really understand how the car's OEM reverse camera works.

Does the reversing camera receive power from the reversing light, and when the camera is on it sends a video signal, and when the head unit receives that signal it switches to "display the reversing camera video" mode?

Or does the head unit receive a 12v signal from the reversing lights, telling it to switch into reverse camera mode, and then the head unit powers and controls the camera?

Like every other Toyota, the reverse camera also displays moving lines showing where you're going to go, based on the steering wheel position. So I take it the head unit also receives some kind of video signal from the body computer that generates those lines on the screen?

Does anyone know where to find pinout diagrams or a how-to for wiring in one of these? Google is not being my friend today.

Richard. there is an adaptor from Toyota 4 wire to generic two wire cameras.but the lines on the screen only ever point backwards with the new fitted stuff.

Reverse camera will actually be 6v.

These guys show how it's done https://www.youtube.com/watch?v=1u7RgCnaer4

Just thinking about this a bit Richard.
Given your car is 20 years old the existing camera will be a similar age.
A new decent quality camera is about $75.00.
Yea its a bit of a pain running the camera wires back (forwards) but its not too much of a major. it will then plug straight into your head unit. The "trigger" is the reverse light. so you tap into the reverse light circuit. You MIGHT be able to just reuse the existing wires to reverse and join to them to save a bunch of wire tracing.

Thanks! Helpful info.